One way the characterize certain classes of -groups is via exact sequences
-group | ||||
---|---|---|---|---|
formal -group | connected | étale | p.34 | |
finite k-group | infinitesimal | étale | splits if is perfect | p.35 |
affine k-group | multiplicative | unipotent | splits if is perfect | p.39 |
connected formal -group | is smooth | is infinitesimal | p. 43 |
(p. 39)
If is perfect any finite affine -group is in a unique way the product of four subgroups
where
is a formal étale multiplicative group.
is a formal étale unipotent group.
is a formal infinitesimal multiplicative group.
is a infinitesimal unipotent group.
affine commutative -group | is affine commutative formal -group | p.27 |
finite commutative -group | finite commutative -group | p.27 |
constant -group | diagonalizable -group | p.36 |
étale k-group | multiplicative k-group | p.37 |
multiplicative k-group | is étale formal -group | p.37 |
unipotent k-group | connected formal group | p.38 |
unipotent | multiplicative | étale | connected | infinitesimal | diagonalizable | |
unipotent | ||||||
multiplicative | ||||||
étale | ||||||
connected | ||||||
infinitesimal | ||||||
diagonalizable |